Tissue factor (TF) is a sedimentable, integral membrane receptor protein with an estimated molecular weight of 42-47 kDa. Peritumor fibrin deposition, which is characteristic of most types of human cancer, is the result of the local expression of potent procoagulants like tissue factor (TF) in tumor cells, tumor-associated macrophages (TAMs) and tumor-associated vascular endothelial cells (VECs). In addition to the importance of TF expression in the pathogenesis of the thrombotic complications common to cancer patients, increasing evidence links TF expression to the regulation of tumor angiogenesis, growth and metastasis. For example, angiogenesis in vivo is inhibited by TF antisense. Further, murine tumor cells transfected to overexpress TF enhance vascular permeability factor (VEGF) transcription and translation. Conversely, tumor cells transfected with TF antisense reduce VEGF transcription and translation. VEGF acts specifically on VECs to promote vascular permeability, endothelial cell growth and angiogenesis, and has been shown to induce expression of TF activity in VECs and monocytes and is chemotactic for monocytes, osteoblasts and VECs. Expression of TF and VEGF in cancer cells is further enhanced under hypoxic condition. Thus, there is evidence to suggest that TF is a key molecule participating in the regulation of VEGF synthesis and, hence, tumor angiogenesis in cancer.
Relatively few compounds exhibiting anti-angiogenic properties useful in the treatment of cancer have been investigated. Curcumin (diferuloylmethane), the aromatic yellow pigment in curry, turmeric and mustard, is known to have anti-angiogenic, anti-tumor, and anti-tumor promoting properties. In addition, curcumin exhibits numerous other therapeutic effects, including anti-oxidative, anti-thrombotic, anti-inflammatory, anti-cholesterol and anti-diabetic properties. Two other compounds that have received considerable attention are genistein, a soybean-derived isoflavone tyrosine kinase C inhibitor, and linomide, a quinoline-3-carboxaminde. Certain flavonoids, such as apigenin, have been shown to be more potent inhibitors of cell proliferation and in vitro angiogenesis than genistein. There remains a need in the art for compounds that exhibit anti-tumor and anti-angiogenic properties for use in cancer therapy.